1. Field of the Invention
The present invention relates to a network interface apparatus arranged to communicate via a network.
2. Description of the Related Art
In recent years, in view of issues such as reduction of CO2 emission, lowering power consumption of electric devices has been socially demanded. For example, in a network device connected to a network such as a LAN, the network device saves power by turning off the power of a CPU or a hard disc and operating only a network interface controller (NIC) that is directly connected to the network.
In such a network device, an information processing device saves power without interfering with a low power consumption mode of units other than a network interface unit even when a status request (status transmitting request command) is transmitted from other network devices. Requests other than the status request are processed via the network with all units other than the network interface unit in a normal power mode. The network interface unit responds to the status request based on status data of the information processing device stored in a storing unit while maintaining all units other than the network interface unit in the low power consumption mode, so as to save power for the entire information processing device.
More specifically, a main CPU obtains its status by reading, for example, a register of a function block, and stores the status in a status storing unit when it is determined that no process is requested. For example, if the information processing device is a printer, a usage status of the printer can be stored. The function block and the main CPU then proceed to the low power consumption mode. Here, all units except the network interface unit are in the low power consumption mode. When the main CPU receives a request from the network device via the network while in the low power consumption mode, a sub-CPU arranged to control the network interface unit determines whether the request is a status request. When the request is not a status request, the main CPU proceeds back to the normal mode through an interrupt signal. The main CPU in the normal mode then causes the function block to proceed back to the normal mode to perform the process in response to the request. In contrast, when the request is a status request (status transmitting request command), the sub-CPU directly transmits a response (status information) to the network by referring to the status storing unit.
The above described information processing device attempts to save power of the device by keeping all units other than the network interface unit in the low power consumption mode and operating only the network interface unit while waiting. Power is saved without interfering with the low power consumption mode of units other than the network interface unit even when it receives a status request (status transmitting request command). However, since the network interface unit needs to be operative at all times to process requests transmitted from other network devices via the network, the network interface unit cannot obtain the lower power consumption mode. Therefore, it becomes difficult to save power of the network interface unit.
Further, in order to analyze the received data and determine whether it is a status request, and then to respond, the network interface unit needs to include, for example, a TCP/IP protocol stack. In order to include the TCP/IP protocol stack, the network interface unit must have a large-capacity memory to store large volumes of programs. Furthermore, in order to perform the analyzing process with the TCP/IP protocol stack, a high-speed CPU with appropriate processing power is required. Operating the large-capacity memory and high-speed CPU at all times increases the power consumption of the network interface unit.